Flat type heat pipe and method of manufacturing the same

ABSTRACT

A method of manufacturing a flat type heat pipe, having an inside of which partitioned into a plurality of cells, that is capable of flexibly setting a concentration of working fluid in each cell is provided. The method includes processes of preparing a flat container, pouring, and closing. In the preparing, the flat container having the inside of which two-dimensionally partitioned into the plurality of cells is prepared. The flat container has connecting holes through which adjacent cells communicate and an inlet hole for the working fluid to be poured from outside. In the pouring, the working fluid is poured into respective cells through the inlet hole and the connecting holes. In the closing, the inlet hole and the connecting holes are closed. In one method, after sealing a specified cell, following processes of heating, removing air, pouring, evaporating, and closing are repeated for other cells.

TECHNICAL FIELD

The present invention relates to a flat type heat pipe and a method of manufacturing the same.

BACKGROUND ART

A heat pipe in which a volatile working fluid is confined in a sealed pipe made of a material with high thermal conductivity (typically, copper or aluminum) is often used. Especially, in order to efficiently cool down a heat-radiating element such as CPU or a power transistor, a flat type heat pipe which ensures large contact area with the heat-radiating element is often used. In order to achieve different heat transferring capabilities depending on areas of the heat pipe, a flat type heat pipe having a flat container partitioned into a plurality of cells, where each cell has a different concentration of a working fluid is proposed (patent document 1).

CITATION LIST Patent Document

Patent Document 1: Japanese Patent Application Publication No. 05-126481

SUMMARY OF INVENTION

In a technique in patent document 1, firstly, a working fluid is poured into cells which mutually communicate. Secondly, the container is tilted to adjust an amount of the working fluid in each cell. Lastly, holes that connect the cells are closed. According to such a method, however, an only possible distribution of the amount of the working fluid is a distribution in which the amount of the working fluid is large on a lower side of tilting and is small on a higher side of the tilting. The present description provides a technique that enables to set a concentration of the working fluid flexibly in each cell.

The present description provides three methods of manufacturing. A first method of manufacturing will be outlined. First, a container having an inside of which partitioned into a plurality of cells is prepared. It is preferable that the container is made of copper or aluminum. Connecting holes through which adjacent cells are communicated are provided in the container. Also, an inlet hole for a working fluid to be poured from outside is provided. That is, all of the cells are not sealed at first. In the first method of manufacturing, air in a non-seal cell is removed, the working fluid is poured into the cells, and the container is heated to evaporate the poured working fluid. If a concentration of the working fluid in a specified cell reaches a desired concentration, the specified cell is sealed. The above processes are repeated and lastly, the inlet hole is closed.

A second method of manufacturing will be outlined. In the second method, a container similar to the container used in the first method is prepared. After preparing the container, respective cells are heated to different temperatures. Then, a working fluid is poured into each cell and evaporated. Then the inlet hole is closed. At this time, connecting holes have not been closed yet. That way, a gas of the working fluid moves among the cells in accordance with a temperature gradient of the cells. As a result, a concentration of the working fluid differs depending on the cells. The connecting holes are closed after the concentrations of the working fluid in the respective cells reach desired concentrations.

In both of the first and the second methods, the inlet hole does not have to be provided for each cell. Although the respective cells are connected via the connecting holes provided on their side walls, the connecting holes can be closed by applying pressure from outside. Flat surfaces of each cell (upper surface and lower surface) do not have to be provided with a hole, so surfaces thereof can be widely used. Further, in the second method, it is possible to manufacture the flat type heat pipe in a short time since no repeating process is required.

A third method of manufacturing will be outlined. In this method, a volume of at least one of the cells is reduced by applying pressure from outside to the at least one of the cells after closing an inlet hole and connecting holes. This method has an advantage of easy manufacturing.

Details of the technique disclosed herein will be explained in the following embodiments of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a perspective view of a flat container.

FIG. 2A shows a diagram to describe a first method of manufacturing (heating and air removing processes).

FIG. 2B shows a diagram to describe the first method of manufacturing (a process of pouring working fluid)

FIG. 2C shows a diagram to describe the first method of manufacturing (an evaporating process).

FIG. 2D shows a diagram to describe the first method of manufacturing (a closing process).

FIG. 2E shows a diagram to describe the first method of manufacturing (secondary heating and air removing processes).

FIG. 2F shows a diagram to describe the first method of manufacturing (a secondary closing process).

FIG. 2G shows a diagram to describe the first method of manufacturing (a completed diagram).

FIG. 3A shows a diagram to describe a second method of manufacturing (a heating process).

FIG. 3B shows a diagram to describe the second method of manufacturing (air removing, and pouring of working fluid processes).

FIG. 3C shows a diagram to describe the second method of manufacturing (evaporating, and closing of an inlet hole processes).

FIG. 3D shows a diagram to describe the second method of manufacturing (a closing of connecting holes process).

FIG. 4A shows a diagram to describe a third method of manufacturing (heating, air removing, and pouring processes).

FIG. 4B shows a diagram to describe the third method of manufacturing (evaporating and closing processes).

FIG. 4C shows a diagram to describe the third method of manufacturing (a reduction of a volume of a cell process).

DESCRIPTION OF EMBODIMENTS Embodiment 1

FIG. 1 shows a perspective view of a container 10. The container 10 comprises a body 4 which is partitioned into a plurality of cells A to I, and a top plate 2 which covers the body 4. The cells A to I are laid out two-dimensionally. The cells A to I are all the same size. An inlet hole 6 is provided on a side wall of the body 4 (a side wall of the cell A).

Also, connecting holes 8 are provided on partition walls which separate the cells. Note that in FIG. 1, a reference sign “8” has only been put to the connecting holes provided on the cell A, and the reference signs for connecting holes of other cells have been omitted. The body 4 and the top plate 2 are made of copper or aluminum. The body 4 is formed by press working The body 4 and the top plate 2 are joined with each other by compressing or brazing. When the body 4 and the top plate 2 are joined, each cell is partitioned from the other cells except for their connecting holes 8. The completed container 10 has the connecting holes 8 through which the adjacent cells communicate as well as one inlet hole 6 on the side wall thereof. Note that an appropriate amount of wick is put in each cell before joining the body 4 and the top plate 2. Description and illustration regarding wick are omitted in the present description.

Next, the first method of manufacturing will be explained (FIG. 2A to FIG. 2G). First, the container shown in FIG. 1 is produced (a preparing process). After heating the container 10 to a predetermined temperature, a pump 21 is connected to the inlet hole 6 to remove air from an inside of the container 10 (FIG. 2A, air removing process). The inside of the container 10 is substantially vacuated by removing air. Second, a working fluid 22 is poured (FIG. 2B, a pouring process). The working fluid, at this time, is volatile liquid. Water or ammonia is used as the working fluid, but other volatile liquid can also be used.

After pouring the working fluid, the process is queued until the working fluid evaporates (FIG. 2C, an evaporating process). The working fluid in the form of a liquid evaporates by being heated by heat of the container. In the embodiment, the process is queued until a concentration of the working fluid in the cell I reaches a concentration desired for the cell I. When the concentration of the working fluid reaches the concentration desired for the cell I, the connecting holes 8 x which communicate the cell I are all closed (FIG. 2D, a closing process). The connecting holes 8 x can be closed, for example, by squashing them from outside. At a step shown in FIG. 2D, the sealed cell I with the desired concentration of the working fluid is achieved.

Next, the container 10 is heated again and air in non-sealed cells (the cell A to the cell H) is removed by the pump 21 (FIG. 2E, a secondary air removing process). Pouring the working fluid (a secondary pouring process) and evaporating the working fluid (a secondary evaporating process) are repeated, and the process is queued until a concentration of the working fluid in the cell H reaches a concentration desired for the cell H. When the concentration of the working fluid reaches the concentration desired for the cell H, the connecting holes 8 y which communicate the cell H are all closed (a secondary closing process). This is how the sealed cell H with the desired concentration of the working fluid is achieved (FIG. 2F). The above processes are repeated until all cells are sealed. That is, in this method of manufacturing, after a specified cell is sealed, processes of heating, air removing, pouring, evaporating, and closing are repeated for other cells. Lastly, when the cell A is sealed, the inlet hole 6 is also closed. As such, a flat type heat pipe 10 having the cells with different concentrations of the working fluid is achieved (FIG. 2G).

Embodiment 2

Next, the second method of manufacturing will be explained (FIG. 3A to FIG. 3D). First, the container 10 is heated. In this method of manufacturing, each cell is heated to a different temperature. For example, a heater is used on each cell to heat each cell individually (FIG. 3A). Then, the pump 21 is connected to the inlet hole 6 to remove air from the container (an air removing process). After that, the working fluid is poured (FIG. 3B, a pouring process). After the working fluid evaporates, only the inlet hole 6 is closed, and the process is queued for a while. At this time, the connecting holes 8 are not closed. Then, the concentrations of the working fluid in the cells change depending on a difference in temperature among the cells (FIG. 3C). The concentration in a cell with high temperature becomes higher than the concentration in a cell with low temperature. Note that, a difference in the concentration is represented by a difference in hatching in FIG. 3C. When the concentration in each cell becomes stable, all of the connecting holes 8 are closed (FIG. 3D, a closing process). As such, the flat type heat pipe 10 having the cells with the different concentrations of the working fluid is achieved (FIG. 3D).

Embodiment 3

Next, the third method of manufacturing will be explained (FIG. 4A to FIG. 4D). The container 10 is heated and the air is removed from the container 10, and the working fluid is poured into the container 10 (FIG. 4A). When the working fluid evaporates, the inlet hole 6 and all of the connecting holes 8 are closed (FIG. 4B). In this method of manufacturing, the concentrations of the working fluid at this point are the same in all of the cells. In this method of manufacturing, then, a part of a cell is squashed to reduce a volume of the cell (FIG. 4C). Note that a lower diagram in FIG. 4C is a cross-sectional view along a IV-IV line in a corresponding top view. A partial area Hd of the cell H and a partial area Id of the cell I are squashed in FIG. 4C. A partial area of a cell other than the cell H and the cell I is also squashed. A size of the area squashed varies depending on the cells. The concentration of the working fluid in a cell can be the desired concentration by squashing a part of the cell to change the volume of the cell.

Points to be noted regarding the technique in the embodiments will be remarked. In the embodiments, the container having a plurality of cells with the same volume is used. The size of the cells may vary.

In the heat pipe in the embodiments, a plurality of cells is two-dimensionally laid out in the container. Here, “a plurality of cells is two-dimensionally laid out” means that the cells are arranged along two directions which define a plane (an x-axis direction and a y-axis direction).

In the first method, the heating of the container is repeated every time one cell has been sealed. As an alternate, the sealing of the cells may be repeated while keeping the container heated. Alternatively, the sealing of the cells may be repeated while maintaining the container at a predetermined temperature.

The connecting hole does not have to be provided between every adjacent two cells. It is enough to secure a passage which leads to each cell from the inlet hole. For example, in the embodiments, the connecting hole between the cell E and the cell D and the connecting hole between the cell D and the cell G may be omitted. This is because the working fluid can be transferred into the cell D through the connecting hole between the cell A and the cell D and because the working fluid can be transferred into the cell G through the connecting hole between the cell H and the cell G.

Either method of manufacturing mentioned above makes it possible to set the concentrations of the working fluid in the cells flexibly, independent of other cells. Also, either method of manufacturing mentioned above provides a flat type heat pipe in which the cells with the different concentrations of the working fluid are two-dimensionally laid out.

Representative, non-limiting examples of the present invention has been be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed herein may be utilized separately or in conjunction with other features and teachings to provide improved flat type heat pipe and methods of manufacturing the same.

Moreover, combinations of features and steps disclosed in the following detail description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.

All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.

Specific examples of the present invention are described above in detail, but these merely illustrate some possibilities of the teachings and do not restrict the scope of the claims. The art set forth in the claims includes variations and modifications of the specific examples set forth above. Further, the technical elements disclosed in the specification or the drawings have technical utility separately or in all types of combinations, and are not limited to the combinations set forth in the claims at the time of filing of the application. Furthermore, the art disclosed in the specification or the drawings may be utilized to simultaneously achieve a plurality of aims, and has technical utility by achieving any one of these aims. 

1. A method for manufacturing a flat type heat pipe, the method comprising: preparing a flat container having an inside of which two-dimensionally partitioned into a plurality of cells, the flat container having connecting holes that communicate adjacent cells to each other and an inlet hole for a working fluid to be poured from outside; pouring the working fluid in the respective cells through the inlet hole and the connecting holes; and closing the inlet hole and the connecting holes.
 2. The method of claim 1, wherein following processes are repeated in the pouring and the closing: removing air from a non-sealed cell; pouring the working fluid into the non-sealed cell; evaporating the poured working fluid; and sealing a specified cell after a concentration of the working fluid in the specified cell reaches a predetermined concentration.
 3. The method of claim 1, wherein: the pouring includes evaporating the working fluid in the cells after heating the respective cells to different temperatures; and the closing includes closing the connecting holes after closing the inlet hole and changing concentrations of the working fluid in the respective cells in accordance with a temperature gradient of the cells.
 4. The method of claim 1, further comprising reducing a volume of at least one of the cells by applying pressure to the at least one of the cells after closing the inlet hole and the connecting holes.
 5. A flat type heat pipe manufactured by the method of claim
 1. 6. A flat type heat pipe in which a plurality of cells with different concentrations of a working fluid is two-dimensionally arranged. 